"Oh, it's all gooey" - after taking a condom out of the wrapper, episode 507, "Proper Condom Use".
"Ah, it's all g-gooey" - after touching the 'lava' from his class volcano project, episode 512, "Here Comes the Neighborhood".
"Oh, it's all sticky" - after sticking his finger into a cow patty, episode 513, "Kenny Dies".
"Ew...they're all hard and oogy" - while poking Wendy's breast after she gets silicone implants, episode 610, "Bebe's Boobs Destroy Society".
"Oh, it's all thick and gooey" - after drinking too much cough medicine, episode 811, "Quest for Ratings".
A common running joke is the song Butters sings, "Loo loo loo, I've got some apples, loo loo loo, You've got some too". Butters is usually interrupted before he can continue the song, but when he does get the opportunity to finish the song, he continues with either, "Loo loo loo, Let's make some applesauce, Take off our clothes and loo loo loo", or alternatively, "Loo loo loo, Let's get together, I know what we can do loo loo". He also seems inordinately fond of the Chicago ballad "If You Leave Me Now".
Butters' theme song, "Everyone Knows It's Butters" (as featured in Butters' Very Own Episode), is loosely based on The Association's 1967 song "Windy", which ends each stanza (except for the chorus) with "Everyone knows it's Windy".
In the same episode, Butters pops through a hole under the title in a way very reminiscent of Porky Pig, an awkwardly comical character who comes from the same tradition as Butters and who originally started out as a school-aged child.
In the second season premiere episode of Veronica Mars, the show introduced a new character named Vincent "Butters" Clemmons, as an homage to the South Park character.
Butters also sang a song about his robot best friend "AWESOM-O" (who is really Cartman in disguise) that goes "Let me tell ya about my robot friend, he's metal and small and doesn't judge me at all".
Butters' birthday is September 11, a sheer coincidence.
Butters and Professor Chaos are also referenced in the song "Peeranoia" by rapper Cage, on his album Hell's Winter.
Butters was molested by his uncle, having received annilingus from him.
In "Erection Day" it is revealed that Butters goes to the toilet by pulling his pants down to his knees and lifting his shirt by his chest which we can guess is a childhood habit that he is still to grow out of.
Butters has also made several appearances in South Park: Bigger, Longer, and Uncut, but he does not play any kind of significant role. He is simply an extra.
In episode 802, AWESOM-O, we learn that Butters wears a diaper to school due to bowel problems. This is probably due to him being abused by his parents.
In the episode Casa Bonita, director of animation Eric Stough's name is credited as Eric Leopold Stotch.